Houston police say the man who shot and killed a fellow employee Friday at the Johnson Space Center before killing himself got a poor job review and feared being fired.
An email citing his job deficiencies was found in his lunch bag.
Police say Friday's shootings at Johnson Space Center began when William Phillips confronted a superior, David Beverly, about his performance review.
Police say the two men talked in Beverly's office for several minutes, then Phillips shot Beverly twice. They say he left, then
returned and shot Beverly two more times.
Police say Phillips also duct-taped a woman to a chair and held her hostage for hours.
NASA says it's reviewing its security procedures.